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05-07-2008, 06:21 PM
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 RE: reliability? Curious, I ran this one using set explain: SELECT MIN(colno) FROM syscolumns WHERE colno>=1 AND colno>1 Estimated Cost: 400 Estimated # of Rows Returned: 1 1) informix.syscolumns: INDEX PATH (1) Index Keys: tabid colno (Key-Only) Index Key Filters: (informix.syscolumns.colno >= 1 ) The AND is being dropped. It would seem that the optimizer looks for simplifications that can be applied and in this case is dropping the more restritive filter. Of course I could be giving the optimizer too much credit. > -----Original Message----- > From: informix-list-bounces@iiug.org > [mailto:informix-list-bounces@iiug.org]On Behalf Of Andrew Ford > Sent: Wednesday, May 07, 2008 10:59 AM > To: informix-list@iiug.org > Subject: Re: reliability? > > > > Same on HPUX 11.11, IDS10.00.FC6 > > > > Not the same result on IDS 11.10.UC1, Red Hat Enterprise > Linux ES release 4. > > > echo "SELECT MIN(colno) FROM syscolumns WHERE colno>=1 AND > colno>1" | > > dbaccess sysmaster > > Database selected. > > > > (min) > > 2 > > 1 row(s) retrieved. > > > > Database closed. > > > Andrew > > > _______________________________________________ > Informix-list mailing list > Informix-list@iiug.org > http://www.iiug.org/mailman/listinfo/informix-list > Notice of Confidentiality: **This E-mail and any of its attachments may contain Lincoln National Corporation proprietary information, which is privileged, confidential, or subject to copyright belonging to the Lincoln National Corporation family of companies. This E-mail is intended solely for the use of the individual or entity to which it is addressed. If you are not the intended recipient of this E-mail, you are hereby notified that any dissemination, distribution, copying, or action taken in relation to the contents of and attachments to this E-mail is strictly prohibited and may be unlawful. If you have received this E-mail in error, please notify the sender immediately and permanently delete the original and any copy of thisE-mail and any printout. Thank You.**      |
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05-07-2008, 06:21 PM
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| Re: reliability? > The AND is being dropped. It would seem that the optimizer looks for > simplifications that can be applied and in this case is dropping the more > > restritive filter. Of course I could be giving the optimizer too much > credit. exectly - just changing the order of filter is enought to change ther result SELECT MIN(colno) FROM syscolumns WHERE colno>1 AND colno>=1 gives 2 |
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